def _build_8k_track(sectors):
if len(sectors) != 1:
return None
c, h, r, n, errs, data = sectors[0]
if n != 6:
return None
if errs.id_crc_error or errs.data_not_found or not errs.data_crc_error:
return None
# Magic longtrack value is for Coin-Op Hits. Taken from SAMdisk.
if len(data) > 6307:
data = data[:6307]
track = EDSKTrack()
t = track.bytes
# Post-index gap
t += mfm.encode(bytes([track.gapbyte] * 16))
# IAM
t += mfm.encode(bytes(track.gap_presync))
t += mfm.iam_sync_bytes
t += mfm.encode(bytes([mfm.IBM_MFM.IAM]))
t += mfm.encode(bytes([track.gapbyte] * 16))
# IDAM
t += mfm.encode(bytes(track.gap_presync))
t += mfm.sync_bytes
am = bytes([0xa1, 0xa1, 0xa1, mfm.IBM_MFM.IDAM, c, h, r, n])
crc = mfm.crc16.new(am).crcValue
am += struct.pack('>H', crc)
t += mfm.encode(am[3:])
t += mfm.encode(bytes([track.gapbyte] * track.gap_2))
# DAM
t += mfm.encode(bytes(track.gap_presync))
t += mfm.sync_bytes
dmark = (mfm.IBM_MFM.DDAM if errs.deleted_dam else mfm.IBM_MFM.DAM)
am = bytes([0xa1, 0xa1, 0xa1, dmark]) + data
t += mfm.encode(am[3:])
return track
def from_file(cls, name):
with open(name, "rb") as f:
dat = f.read()
edsk = cls()
sig, creator, ncyls, nsides, track_sz = struct.unpack(
'<34s14s2BH', dat[:52])
if sig[:8] == b'MV - CPC':
extended = False
elif sig[:16] == b'EXTENDED CPC DSK':
extended = True
else:
raise error.Fatal('Unrecognised CPC DSK file: bad signature')
if extended:
track_sizes = list(dat[52:52+ncyls*nsides])
track_sizes = list(map(lambda x: x*256, track_sizes))
else:
track_sizes = [track_sz] * (ncyls * nsides)
o = 256 # skip disk header and track-size table
for track_size in track_sizes:
if track_size == 0:
continue
sig, cyl, head, sec_sz, nsecs, gap_3, filler = struct.unpack(
'<12s4x2B2x4B', dat[o:o+24])
error.check(sig == b'Track-Info\r\n',
'EDSK: Missing track header')
error.check((cyl, head) not in edsk.to_track,
'EDSK: Track specified twice')
bad_crc_clip_data = False
while True:
track = EDSKTrack()
t = track.bytes
# Post-index gap
t += mfm.encode(bytes([track.gapbyte] * track.gap_4a))
# IAM
t += mfm.encode(bytes(track.gap_presync))
t += mfm.iam_sync_bytes
t += mfm.encode(bytes([mfm.IBM_MFM.IAM]))
t += mfm.encode(bytes([track.gapbyte] * track.gap_1))
sh = dat[o+24:o+24+8*nsecs]
data_pos = o + 256 # skip track header and sector-info table
clippable, ngap3, sectors, idam_included = 0, 0, [], False
while sh:
c, h, r, n, stat1, stat2, data_size = struct.unpack(
'<6BH', sh[:8])
sh = sh[8:]
native_size = mfm.sec_sz(n)
weak = []
errs = SectorErrors(stat1, stat2)
num_copies = 0 if errs.data_not_found else 1
if not extended:
data_size = mfm.sec_sz(sec_sz)
sec_data = dat[data_pos:data_pos+data_size]
data_pos += data_size
if (extended
and data_size > native_size
and errs.data_crc_error
and (data_size % native_size == 0
or data_size == 49152)):
num_copies = (3 if data_size == 49152
else data_size // native_size)
data_size //= num_copies
weak = cls().find_weak_ranges(sec_data, data_size)
sec_data = sec_data[:data_size]
sectors.append((c,h,r,n,errs,sec_data))
# IDAM
if not idam_included:
t += mfm.encode(bytes(track.gap_presync))
t += mfm.sync_bytes
am = bytes([0xa1, 0xa1, 0xa1, mfm.IBM_MFM.IDAM,
c, h, r, n])
crc = mfm.crc16.new(am).crcValue
if errs.id_crc_error:
crc ^= 0x5555
am += struct.pack('>H', crc)
t += mfm.encode(am[3:])
t += mfm.encode(bytes([track.gapbyte] * track.gap_2))
# DAM
gap_included, idam_included = False, False
if errs.id_crc_error or errs.data_not_found:
continue
t += mfm.encode(bytes(track.gap_presync))
t += mfm.sync_bytes
track.weak += [((s+len(t)//2+1)*16, n*16) for s,n in weak]
dmark = (mfm.IBM_MFM.DDAM if errs.deleted_dam
else mfm.IBM_MFM.DAM)
if errs.data_crc_error:
if sh:
# Look for next IDAM
idam = bytes([0]*12 + [0xa1]*3
+ [mfm.IBM_MFM.IDAM])
idx = sec_data.find(idam)
else:
# Last sector: Look for GAP3
idx = sec_data.find(bytes([track.gapbyte]*8))
if idx > 0:
# 2 + gap_3 = CRC + GAP3 (because gap_included)
clippable += data_size - idx + 2 + gap_3
if bad_crc_clip_data:
data_size = idx
sec_data = sec_data[:data_size]
gap_included = True
elif data_size < native_size:
# Pad short data
sec_data += bytes(native_size - data_size)
elif data_size > native_size:
# Clip long data if it includes pre-sync 00 bytes
if (sec_data[-13] != 0
and all([v==0 for v in sec_data[-12:]])):
# Includes next pre-sync: Clip it.
sec_data = sec_data[:-12]
if sh:
# Look for next IDAM
idam = bytes([0]*12 + [0xa1]*3 + [mfm.IBM_MFM.IDAM]
+ list(sh[:4]))
idx = sec_data.find(idam)
if idx > native_size:
# Sector data includes next IDAM. Output it
# here and skip it on next iteration.
t += mfm.encode(bytes([dmark]))
t += mfm.encode(sec_data[:idx+12])
t += mfm.sync_bytes
t += mfm.encode(sec_data[idx+12+3:])
idam_included = True
continue
# Long data includes CRC and GAP
gap_included = True
if gap_included:
t += mfm.encode(bytes([dmark]))
t += mfm.encode(sec_data)
continue
am = bytes([0xa1, 0xa1, 0xa1, dmark]) + sec_data
crc = mfm.crc16.new(am).crcValue
if errs.data_crc_error:
crc ^= 0x5555
am += struct.pack('>H', crc)
t += mfm.encode(am[3:])
if sh:
# GAP3 for all but last sector
t += mfm.encode(bytes([track.gapbyte] * gap_3))
ngap3 += 1
# Special track handlers
special_track = cls()._build_8k_track(sectors)
if special_track is None:
special_track = cls()._build_kbi19_track(sectors)
if special_track is not None:
track = special_track
break
# The track may be too long to fit: Check for overhang.
tracklen = int((track.time_per_rev / track.clock) / 16)
overhang = int(len(t)//2 - tracklen*0.99)
if overhang <= 0:
break
# Some EDSK tracks with Bad CRC contain a raw dump following
# the DAM. This can usually be clipped.
if clippable and not bad_crc_clip_data:
bad_crc_clip_data = True
continue
# Some EDSK images have bogus GAP3 values. Shrink it if
# necessary.
new_gap_3 = -1
if ngap3 != 0:
new_gap_3 = gap_3 - math.ceil(overhang / ngap3)
error.check(new_gap_3 >= 0,
'EDSK: Track %d.%d is too long '
'(%d bits @ GAP3=%d; %d bits @ GAP3=0)'
% (cyl, head, len(t)*8, gap_3,
(len(t)//2-gap_3*ngap3)*16))
#print('EDSK: GAP3 reduced (%d -> %d)' % (gap_3, new_gap_3))
gap_3 = new_gap_3
# Pre-index gap
track.verify_len = len(track.bytes)*8
tracklen = int((track.time_per_rev / track.clock) / 16)
gap = max(40, tracklen - len(t)//2)
track.bytes += mfm.encode(bytes([track.gapbyte] * gap))
# Add the clock buts
track.bits = bitarray(endian='big')
track.bits.frombytes(mfm.mfm_encode(track.bytes))
# Register the track
edsk.to_track[cyl,head] = track
o += track_size
return edsk
def addcrc(t,n):
crc = mfm.crc16.new(mfm.decode(t[-n*2:])).crcValue
t += mfm.encode(struct.pack('>H', crc))
def _build_kbi19_track(sectors):
ids = [0,1,4,7,10,13,16,2,5,8,11,14,17,3,6,9,12,15,18]
if len(sectors) != len(ids):
return None
for s,id in zip(sectors,ids):
c,h,r,n,_,_ = s
if r != id or n != 2:
return None
def addcrc(t,n):
crc = mfm.crc16.new(mfm.decode(t[-n*2:])).crcValue
t += mfm.encode(struct.pack('>H', crc))
track = EDSKTrack()
t = track.bytes
# Post-index gap
t += mfm.encode(bytes([track.gapbyte] * 64))
# IAM
t += mfm.encode(bytes(track.gap_presync))
t += mfm.iam_sync_bytes
t += mfm.encode(bytes([mfm.IBM_MFM.IAM]))
t += mfm.encode(bytes([track.gapbyte] * 50))
for idx, s in enumerate(sectors):
c,h,r,n,errs,data = s
# IDAM
t += mfm.encode(bytes(track.gap_presync))
t += mfm.sync_bytes
t += mfm.encode(bytes([mfm.IBM_MFM.IDAM, c, h, r, n]))
addcrc(t, 8)
if r == 0:
t += mfm.encode(bytes([track.gapbyte] * 17))
t += mfm.encode(b' KBI ')
else:
t += mfm.encode(bytes([track.gapbyte] * 8))
t += mfm.encode(b' KBI ')
t += mfm.encode(bytes([track.gapbyte] * 9))
# DAM
t += mfm.encode(bytes(track.gap_presync))
t += mfm.sync_bytes
dmark = (mfm.IBM_MFM.DDAM if errs.deleted_dam
else mfm.IBM_MFM.DAM)
t += mfm.encode(bytes([dmark]))
if idx%3 != 0:
t += mfm.encode(data[:61])
elif r == 0:
t += mfm.encode(data[:512])
addcrc(t,516)
else:
t += mfm.encode(data[0:0x10e])
addcrc(t,516)
t += mfm.encode(data[0x110:0x187])
addcrc(t,516)
t += mfm.encode(data[0x189:0x200])
addcrc(t,516)
t += mfm.encode(bytes([track.gapbyte] * 80))
return track
